Synthetic resin bottles, representatives of which are polyethylene terephthalate (PET) bottles and polypropylene (PP) bottles, are used in various fields, such as beverages, foods, cosmetics, and so forth. Such a container is generally formed in a predetermined shape by fitting a preform in a blow molding mold and by supplying a pressurized fluid from a blow molding device into the preform. The resin preform has been formed in a bottomed tubular shape by, for example, injection molding.
One example of such a blow molding device is the one that uses air or a liquid as the pressurized fluid that is to be filled into the preform. In this case, by using a content liquid, such as a beverage, a cosmetic product, and a pharmaceutical product, that is to be filled in a final product as the liquid, the step of filling the content liquid to the container may be omitted, and the production process and the configuration of the blow molding device may be simplified. Patent Literature 1, for example, describes a method of molding a plastic container, the method including placing a preform, after heated to a predetermined, temperature, in a blow mold and stretch the preform in the blow mold by using a stretching rod, and subsequently filling a liquid, after heated to a predetermined temperature, into the stretched preform to expand the preform, thereby molding the plastic container whose outer shape conforms to an inner circumferential surface the blow mold.